Covered stent with side branch

ABSTRACT

A system for treating stenosis in a target blood vessel, such as the common carotid artery, comprising a graft portion having a main portion and a branch portion extending therefrom. The branch portion extends from the intermediate portion of the main portion at an angle thereto and is in fluid communication with the main portion. A first stent is associated with the main portion and is expandable from a first configuration to a second configuration to retain the main portion in position within the target vessel. A second stent is associated with the branch portion and is expandable from a first configuration to a second configuration to retain the branch portion in position within a branching vessel. In one embodiment, the branch portion is integral with the main portion. In an alternate embodiment the branch portion is connected to the main portion.

This application claims priority from provisional patent applicationSer. No. 60/240,009, filed Oct. 13, 2000 and provisional patentapplication Ser. No. 60/278,361, filed Mar. 23, 2001, the entirecontents of both applications incorporated herein by reference.

BACKGROUND

1. Technical Field

This application relates to a vascular stent and graft and moreparticularly to a covered stent having a side branch to accommodate abranching vessel.

2. Background of Related Art

The vascular disease of arteriosclerosis, also referred to as hardeningof the arteries, is caused when fatty substances and plaque build upinside the artery walls over time and reduce the size of the arteriallumen (passageway), thereby restricting proper blood flow through theartery. This buildup which causes restriction of the vessel is calledstenosis.

The right and left common carotid arteries arise from the aorta and arethe principal blood supply to the head and neck. Each of the two commonarteries divides to form external and internal carotid arteries tosupply the blood to the head and neck. Arteriosclerosis of the carotidarteries if left untreated, will constrict the arterial passageway tosuch an extent as to prevent adequate supply of blood to the brain orultimately will fully occlude the artery to cut off blood flow entirely,causing a stroke resulting in paralysis or even death.

Several methods are currently being utilized to treat arteriosclerosisof the carotid arteries. One method is an invasive surgical procedurewhere the vessel wall is cut open and the portion containing the plaqueis removed. This procedure is traumatic, complex, and requires a longrecovery time for the patient. It also results in weakening of thevessel wall since a portion of the wall is removed. A weakened wall canpotentially result in an aneurysm which is a dilatation (expansion) ofthe artery, which adversely affects vessel function and if notsurgically treated could be life threatening to the patient.

With the advent of minimally invasive procedures, and particularlyintraluminal (within the vessel) procedures for many types of surgeriesin order to reduce trauma to the patient, decrease morbidity, reduce thepatient recovery time and reduce hospital costs, the industry has beenattempting to develop ways to minimally invasively treatarteriosclerosis of the carotid arteries. Initially, balloonangioplasty, a procedure used for treating coronary arteries, wasattempted. In angioplasty, a balloon is placed in the stenosed(restricted) portion or the vessel and inflated to fissure and compressthe plaque against the vessel (arterial) wall, thereby increasing theopening in the vessel to improve blood flow. However, angioplasty of thecarotid arteries was found to create grave risks because plaque, ratherthan just being compressed, could inadvertently be dislodged from thearterial wall and travel up through the internal carotid artery to thebrain, causing a stroke.

To help maintain the enlarged opening created by an angioplasty balloonin coronary arteries, stenting has become widespread. Stenting involvesthe placement of a structural support (a stent), typically composed ofmetal, in the stenosed region either after balloon angioplasty iscompleted or in conjunction with the angioplasty. The stent is expandedin the vessel to provide a radial force against the vessel wall in anattempt to maintain the opening in the vessel created by the angioplastyballoon and overcome the elastic recoil which occurs after balloonangioplasty. Although stents may reduce the chance of dislodgement andflow of plaque to the brain, stents provide their own risks. Forexample, thrombus can build on the stent structure over time, which caneventually become dislodged and travel through the internal carotidarteries to the brain causing embolic stroke. Also, intimal hyperplasia(buildup of scar tissue) around the stent can occur, resulting inrestenosis (re-constriction of the vessel) within or juxtaposed to thestent.

To avoid the flow of dislodged plaque or thrombotic material to thebrain, covered stents have begun to be utilized in the common carotidarteries. The stents are covered with graft material, such as PTFE, andcompressed against the vessel (arterial) wall, thereby sandwiching anydislodged plaque between the graft and vessel wall to preventdislodgement. Thrombotic material can also be captured between the graftand wall. Although these covered stents reduce the dislodgement problemdiscussed above, the placement of the graft material can create otherproblems. If the covered stent is placed in a portion of the commoncarotid artery which does not have any vessels branching off, blood flowis maintained. However, problems can arise if the stenosis is adjacentto a branching vessel because implantation of the covered stent willrequire closing off or blood flow to the branching vessel as the graftmaterial will extend past the branch opening. For example, if the graftof a covered stent is placed in the common carotid artery extending intothe internal carotid artery, the graft will cover the juncture of theexternal carotid artery, thereby cutting off blood flow through theexternal carotid artery to the face and scalp and occluding potentiallylife saving collateral blood supply to the brain. Thus, although theproblems associated with the stenosis in the common carotid artery mightbe alleviated by the covered stent, the patient may still have reducedblood flow because the external carotid artery will no longer be able tosupply collateral blood to the brain if the stent were to fail. Sincethe overall blood flow is reduced, the likelihood of stroke willincrease.

Additionally, by cutting off the opening to the external carotid artery,future access to this artery for treatment is prevented. Therefore, ifan aneurysm or stenosis develops in this artery, the covered stent wouldprevent intraluminal access to the target region.

It would therefore be advantageous to provide a covered stent that couldbe used in the carotid arteries which would not adversely affect bloodflow in branching vessels. Such covered stent would therebyadvantageously enlarge the restriction (stenosis) in the common carotidartery to improve blood flow therethrough without disadvantageouslyreducing blood flow or restricting access to connecting arteries.

SUMMARY

The present invention overcomes the disadvantages and deficiencies ofthe prior art. The present invention provides a system for treatingstenosis in a target blood vessel comprising a graft portion having amain portion and a branch portion extending therefrom. The branchportion extends from the intermediate portion of the main portion at anangle thereto and is in fluid communication with the main portion. Afirst stent is associated with the main portion and is expandable from afirst configuration to a second configuration to retain the main portionin position within the target vessel. A second stent is associated withthe branch portion and is expandable from a first configuration to asecond configuration to retain the branch portion in position within abranching vessel.

In one embodiment, the branch portion is integral with the main portion.In an alternate embodiment the branch portion is connected to the mainportion. In this embodiment, the intermediate portion has an openingtherethrough and the branch portion preferably includes a flange at aproximal end having a diameter greater than a diameter of the opening tothereby retain the flange within the main portion. In another alternateembodiment, the main and branch portions are formed by a bifurcatedgraft.

The ends of the main graft portion and branch graft portion may have aplurality of petals to reduce the radial force against the vessel walls.The petals preferably flare out to a larger diameter than the otherportions of the graft.

In one embodiment, the first and second stents are positioned within themain and branch portions, respectively, so the main and branch portionsexpand upon expansion of their respective stents. In another embodiment,the first and second stents overlie the main and branch graft portions.

In another embodiment, the main and branch portions include alongitudinally extending spine and a plurality of curved ribs extendingfrom the spine. The ribs preferably terminate at first and second tipswhich interleave with first and second tips of adjacent ribs. In anotherembodiment, the main and branch portions include a series of spinesspaced axially and radially with respect to each other.

The present invention also provides a stent for treating a stenosis in atarget blood vessel comprising an expandable stent having an enlargedopening in the intermediate portion configured to allow unobstructedpassage of blood into the main lumen of the stent. The opening isaligned with a vessel branching off the target vessel to maintain flowbetween the target vessel and the branching vessel. The stent mayinclude a graft associated therewith having an opening aligned with theopening in the intermediate portion of the stent to allow passage ofblood. The opening in the intermediate portion of the stent and theopening in the graft can be configured to receive a second grafttherethrough so that the second graft extends outwardly through theopenings at an angle to the first graft.

The present invention also provides a method of implanting first andsecond stents with associated grafts within first and second vesselportions extending at an angle with respect to each other. The methodcomprises

-   -   inserting a first guidewire to guide a first stent with an        associated first graft to a target region of a first vessel;    -   inserting a second guidewire to guide a second stent with an        associated second graft to a second vessel branching from the        first vessel;    -   inserting a delivery device containing the first stent with the        associated first graft over the guidewire to the target vessel        region;    -   removing the delivery device to enable the first stent with the        associated first graft to expand against the wall of the target        vessel;    -   inserting a second delivery device containing a second stent        with the associated second graft over the second guidewire to        the second vessel; and    -   removing the delivery device to enable the second stent with the        associated second graft to expand against the wall of the second        vessel and fluidly communicate with the first stent and        associated graft.

The present invention also provides a specific method of implantingfirst and second stents with associated first and second grafts withinthe carotid artery so the first graft extends from the common carotidartery into the internal carotid artery, past the juncture of the commoncarotid artery and the external carotid artery, and the second graft ispositioned in the external carotid artery thereby maintaining flowbetween the common carotid artery and the external carotid artery.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiment(s) of the present invention are described hereinwith reference to the drawings wherein:

FIG. 1A is a side view of a first embodiment of the covered stent of thepresent invention implanted in the right common and internal carotidarteries and having an integral branch extending into the right externalcarotid artery;

FIG. 1B is a side view of an alternate embodiment of the covered stentimplanted in the right common and internal carotid arteries and having abifurcation to branch into the right external carotid artery;

FIG. 1C illustrates the covered stent of FIG. 1A positioned over thefirst and second guidewires (the delivery sheath not shown for clarity);

FIG. 1D illustrates the covered stent of FIG. 1B positioned over thefirst and second guidewires (the delivery sheath not shown for clarity};

FIG. 2A is a perspective view of another embodiment of the covered mainstent of the present invention having an opening in a sidewall toreceive a covered branch stent therethrough;

FIG. 2B is a perspective view of the covered stent of FIG. 2 shownrotated to align the opening with the branching vessel;

FIG. 3 is a perspective view of yet another embodiment of the coveredstent of the present invention having an opening in a sidewall toreceive a covered branch stent and further having an unsupportedextension;

FIG. 4 is a perspective view of a first embodiment of the covered branchstent insertable into the side opening of the covered stent of FIGS. 2or 3 and having a flange with petals:

FIG. 5 is a front elevation view of the radiopaque disc positioned onthe covered stent of FIGS. 2 and 3;

FIG. 6 is a side elevation view of the radiopaque disc of FIG. 5;

FIG. 7 is a perspective view of second embodiment of the covered branchstent of the present invention insertable into the side opening of thecovered stent of FIGS. 2 or 3 and having smooth proximal and distalends;

FIGS. 8-9 are side views illustrating delivery of the covered main stentand branch stent of FIGS. 2 and 4 within the left carotid arteries,wherein

FIG. 8A illustrates a first guidewire inserted through the left commonand internal carotid arteries past the region of stenosis;

FIG. 8B illustrates the delivery sheath for the covered main stentpositioned over the first guidewire in the left common and internalarteries and a second guidewire extending through the longitudinal slotin the sheath into the left external carotid artery;

FIG. 9A illustrates the delivery sheath for the covered main stent beingwithdrawn to place the covered main stent in the common and internalcarotid arteries and further showing the second guidewire extendingthrough the side opening;

FIG. 9B illustrates the delivery sheath for the covered main stent fullywithdrawn to position the covered main stent in the common and internalcarotid arteries and further showing the delivery sheath for the coveredbranch stent partially withdrawn to place the covered branch stent inthe external carotid artery; and

FIG. 9C illustrates the delivery sheath for the covered branch stentfully withdrawn from the body to position the covered branch stent ofFIG. 4 in the external carotid artery;

FIG. 10 illustrates a covered branch stent having petals at its distalend and a smooth proximal end, positioned in the left external carotidartery and connected through the side opening to the covered main stent;

FIG. 11 illustrates the covered main stent of FIG. 3 positioned in theleft common and internal carotid arteries with the second guidewireextending through the side opening for guiding the branch stent;

FIGS. 12A and 12B are perspective and cross sectional views,respectively, of a stent and graft arrangement of the present inventionwherein the stent is positioned outside the graft;

FIGS. 13A and 13B are perspective and cross sectional views,respectively, of a stent and graft arrangement of the present inventionwherein the stent is positioned inside the graft;

FIGS. 14A and 14B are perspective and cross sectional views,respectively, of a stent and graft arrangement of the present inventionwherein the graft is positioned on both the inside and outside of thestent;

FIG. 15 is a perspective view of a stent of the present invention havingan enlarged sidewall opening to accommodate blood flow from a branchingvessel;

FIG. 16 is a side view of an alternate embodiment of the presentinvention illustrating a pair of coils utilized to accommodate abranching vessel;

FIG. 17 is an exploded view of the pair of coils of FIG. 16.

FIG. 18 is a perspective view of another alternate embodiment of thepresent invention illustrating a bifurcated stent, with overlappingribs, to accommodate a branching vessel;

FIG. 19 is a perspective view of another alternate embodiment of thebifurcated stent having non-aligned interleaving ribs;

FIG. 20A is a perspective view of a segment of yet another alternateembodiment of the bifurcated stent having a staggered supporting spineto provide uniform rigidity;

FIG. 20B is a side view of the stent of FIG. 20A;

FIG. 21A is a perspective view of another alternate embodiment of thebifurcated stent having a helical configuration to form a spring-likeelement; and

FIG. 21B is a side view of the stent of FIG. 21A;

FIG. 22 is a perspective view of an alternative approach to accommodatea branching vessel which utilizes, as shown, a pair of juxtaposedcovered stents with angled adjacent ends to accommodate blood flow froma branching vessel; and

FIG. 23 is a perspective view of an alternative approach to accommodatea branching vessel, similar to FIG. 22, except utilizing a singlecovered stent with an angled end to accommodate blood flow from abranching vessel.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now in detail to the drawings wherein like reference numeralsidentify similar or like components throughout the several views,several embodiments of covered stents are illustrated to accommodate abranch of a target vessel. The covered stent includes a side branch,which can be either integral as shown in FIGS. 1A and 1B or a separate“branch” stent attached to a “main” stent as shown in FIGS. 2-4 and 7.The side branch extends into a vessel branching from the target vessel.The stent functions to expand the constricted passage, i.e. thestenosis, created by plaque buildup inside the vessel wall. A graft,composed of material such as PTFE or other known materials, ispositioned over the stent (referred to as a “covered stent”), as shownin FIGS. 13A and 13B, so when the stent is expanded the graft is pushedagainst and retained against the inside vessel wall, thereby compressingthe plaque, which might otherwise become dislodged, between the graftand the vessel wall. The stent retains the graft in place which createsa passageway for blood flow.

Currently, a covered stent having only a longitudinal directionalcomponent is placed inside the vessel wall. However, if the coveredstent is placed adjacent a branching vessel, then that branching vesselwill be closed off, preventing blood flow therethrough. For example, ifin treating stenosis in the common carotid artery, a covered stent isplaced in the common carotid artery extending to the internal carotidartery, the graft will extend past the juncture of the external carotidartery, thereby undesirably blocking blood flow to the external carotidartery. The covered stent of the present invention has an angled sidebranch which extends into the branching vessel, e.g. the externalcarotid artery, thereby allowing blood flow through the branching vesselwhich would otherwise be blocked if an elongated covered stent wasplaced in the artery across the juncture.

The covered stent of the present invention is described herein for usein carotid arteries by way of example. However, it should be understoodthat it is contemplated that the stent can be utilized in other vesselssuch as the coronary arteries, the descending aorta and renal arteries,the external iliac and internal iliac arteries and the common femoraland deep femoral arteries. Thus, the covered stent of the presentinvention, as can be appreciated, has application for vessels where astenosis is adjacent a branching vessel. The covered stent of thepresent invention can also be utilized for other vascular procedureswhere it would extend past the juncture of the target vessel and abranching vessel.

With reference now to FIGS. 1A-1D, and with reference to use in thecarotid arteries by way of example, two embodiments of the covered stentof the present invention having an integral side branch are disclosed.In the first embodiment, shown in FIG. 1A, covered stent 10 includes agraft 12 and an underlying main stent 20 and branch stent 22, onlypartially and schematically shown for clarity. Graft 12 includes a mainportion 16 and a side branch portion 18 integral therewith. Main stent20 underlies main graft portion 16 and branch stent 22 underlies sidebranch graft portion 18. Side branch portion 18 extends from anintermediate portion 17 of the covered stent 10 as shown. The branchportion 18 ensures that blood can continue to flow through the rightexternal carotid artery “c”, in the direction of the arrows, once thegraft portions 16, 18 and underlying stents are positioned in the rightcommon carotid artery “a”, right internal carotid artery “b”, and rightexternal carotid artery “c”.

FIG. 1B illustrates an alternate embodiment of the covered stent havingan integral branch portion. Covered stent 30 includes a graft 31bifurcated at its distal end portion 32 to form a first or main graftleg 34 and a second or side (branch) graft leg 36. Stent 40 underliesmain leg 34 and stent 42 underlies side leg 36. Like covered stent 10,covered stent 30 is shown positioned to treat a stenosis in the rightcommon carotid artery “a” with the main leg 34 extending into theinternal carotid artery “b” and the side leg 36 extending into the rightexternal carotid artery “c”. It should be appreciated that thebifurcated covered stent 30 of FIG. 1B is more versatile in that it canaccommodate various anatomies. The presence of gap “g” adjacent thebifurcation does not affect the desired blood flow.

Grafts 12 and 31 have petals at their ends as shown, the function ofwhich is described below in conjunction with alternate embodiments.

Covered stents 10 and 30 are inserted in similar manners with FIG. 1Cdepicting insertion of covered stent 10 and FIG. 1D depicting insertionof covered stent 30. Two separate guidewires 43, 45 are insertedintraluminally, one extending through the right common carotid artery“a” into the internal carotid artery “b” and the other extending throughthe right common carotid artery into the external carotid artery “c”.The covered stent 10 or 30 has its respective side branch graft portion18 or side graft leg 36 folded towards the main graft portion 16 or maingraft leg 34. The covered stent with the folded branch is then placed ina delivery catheter or sheath (not shown) with the stents positionedover the respective guidewires. The delivery catheter is advancedintraluminally to the target region, and then withdrawn, allowing thebranch portion 18 or side leg 36 to unfold into the external carotidartery “c” and the respective stents 20,22 and 40,42 to expand to alarger diameter configuration. In the larger configuration, the stentsapply a radial force against the vessel wall, thereby retaining thegraft 12 or 31 against the vessel wall. As can be appreciated, blood cancontinue to flow through the graft from the common carotid arterythrough the external carotid artery FIGS. 2-7 illustrate a differentapproach for accommodating the vessel branch. Instead of an integralbranch as in FIGS. 1A and 1B, a separate covered stent branch isattached, preferably in situ, to the covered main stent. Morespecifically, and initially with reference to FIG. 2A, a covered mainstent 50 is illustrated comprising a graft 52 and an underlying stent57. It should be noted that in FIGS. 1-11, the stent is shownschematically and only partially for the sake of clarity. In allembodiments, the underlying stent can extend the length of the graft oronly along part or its length. Also, more than one stent can be utilizedto retain the main graft portion and to retain the branch graft portion.Additionally, the stent can be composed of metallic or polymericmaterial, and include an opening in an intermediate portion to alignwith the opening in the graft as described below.

Referring back to FIG. 2A, graft 52 includes an opening 54 in itssidewall, in an intermediate portion, to accommodate a branch stentdescribed below. Radiopaque discs or markers 55 are positioned adjacentthe side opening 54 to facilitate locating the opening 54 during surgeryto in turn facilitate attachment of the branch stent. Although discshaped, other shaped radiopaque markers or other indicators at variouslocations can be used to facilitate proper orientation of the opening54. Leaflets or petals 56, 58 are positioned on the distal and proximalend portions 60, 62, respectively, of graft 52 to reduce stress on thevessel wall by reducing the radial force against the wall. FIG. 2Billustrates how the covered stent 50 can be rotated to orient the sideopening 54 towards the branching vessel. Side opening 54 has a diameter“A” dimensioned to receive a branch stent as discussed below. The stent57 also includes an opening, such as that shown in FIG. 15, which alignswith the side opening 54 in graft 52 to ensure blood flow therethrough.

FIG. 3 illustrates an alternate embodiment of the covered main stent,designated by reference numeral 70. Covered stent 70 is similar to stent50 in that it has an underlying metallic stent 75 and a graft 73 havinga radiopaque indicator discs 77, side opening 76 having diameter “A” toreceive a branch stent, and petals 74, 78. However, covered stent 70additionally has an extension 72 at a distal end, which is unsupportedby stent 75. This unstented extension reduces the radial force againstthe vessel wall in that region and may also allow placement of a portionof the graft in a vessel region where stenting is ill advised. Stent 75also includes an opening (not shown) in a sidewall to align with sideopening 76 of graft 73.

A first embodiment of the independent covered branch stent, illustratedin FIG. 4, is designated by reference numeral 80 and has a graft 81 andunderlying stent 87. Graft 81 has a first end portion 82, a flange 84 ata second end portion 86, and a waist or reduced diameter portion 88.Underlying stent 87 would similarly have a conforming narrowed portionor otherwise configured or designed so that upon expansion, graft 81retains its waist 88. As indicated, waist 88 has an external diameter“A”, equal to the diameter of the opening 54 or 76 in the sidewall ofcovered main stents 50 or 70. The flange 84 and the portion of thecovered stent distal of the waist 88 have diameters larger than diameter“A” to ensure the covered branch stent 80 does not slip through or outof opening 54 or 76 in covered main stent 50 or 70, respectively. Petalsor leaflets 83, 85 function to reduce the radial force as describedabove.

FIG. 7 illustrates an alternate embodiment of the covered branch stenthaving a graft 91 and underlying stent 97. Branch stent 90 has a flange94 with a smooth portion 95 and a smooth distal end 92. Waist portion 98has a diameter “A” less than diameter “B” and equal to the diameter “A”of the opening 54 or 76 of covered main stents 50 or 70. The largerdiameter “B” and the larger diameter of the flange 94 ensure the branchstent 90 is retained within the covered main stent.

The method of inserting the covered stent of the present invention inthe left carotid arteries will now be described with reference to FIGS.8A-9C. A first guidewire 120 is inserted through the common carotidartery, preferably through an entry point in the femoral artery, andextends to the internal carotid artery as shown in FIG. 8A, past thetarget region of stenosis having plaque “P”. A second guidewire 122extends through the common carotid artery into the external carotidartery. (An angioplasty balloon (not shown) is introduced over theguidewire 120 to pre-dilate the vessel). A delivery catheter or sheath130 containing the covered main stent 50 of FIG. 2A therein, is threadedover the guidewire as shown in FIG. 8B, with the proximal end of theguidewire 120 extending beyond the proximal end 132 of the sheath 130.The main covered stent is thus positioned inside the sheath 130 and overthe guidewire 122. Sheath 130 has a longitudinally extending slot 134,of sufficient size to accommodate a second guidewire 122. The slot 134extends a sufficient distance proximally so at least a portion of theslot is in alignment with the external carotid artery “c” as shown. Thisallows withdrawal of the sheath 130 as described below. Once the sheath130 is advanced into the internal carotid artery “b” so the coveredstent 50 is aligned with the target vessel region, i.e. the portion ofthe vessel having the stenosis, the sheath 130 is withdrawn in thedirection of arrow D in FIG. 9A, thereby allowing the stent 57 to expandto press the graft 52 against the vessel wall. The stent is preferablycomposed of shape memory material, such as Nitinol, that expands from asmaller configuration to its larger memorized configuration inside thebody. As the sheath 130 is pulled proximally, the second guidewire 122remains in place within the external carotid artery. The longitudinalslot 134 allows for this proximal movement without interfering with theguidewire 122.

Upon full withdrawal of the sheath 130, leaving the covered main stent50 positioned as shown in FIG. 9B, the sheath 130 is removed from thepatient, leaving the second guidewire 122 in place as shown. Note thatwith the visual aid (e.g. X-ray) of the radiopaque markers, the coveredmain stent 50 can be rotated, if necessary, to ensure alignment of theopening 54 with the lumen (passageway) of the branching external carotidartery “c”.

A second delivery catheter or sheath 140, containing the covered branchstent 80 of FIG. 4 is then inserted over the second guidewire 122 andthrough the expanded covered main stent 50, exiting through opening 54and into the branching vessel, e.g. the common carotid artery. (FIG. 9B)The sheath 140 is withdrawn proximally allowing the covered branch stent80 to expand against the vessel wall. Note that only a portion of thecovered branch stent 80 is advanced through the side opening 54, leavingthe flanged proximal portion within the interior of the covered mainstent 50, (see FIG. 9C) abutting the internal walls of the main stent 50adjacent the side opening 54, to ensure the branch stent 80 does notbecome detached.

The sheath 140 is then fully withdrawn and removed from the body,allowing the stent 87 to expand and press the graft 81 against the wallof the external carotid artery as shown in FIG. 9C. (The stent 87 isalso preferably composed of shape memory material and expands to itsmemorized configuration) Note that the diameter of the distal end 60 ofthe graft 52 is smaller than the diameter of the proximal end 62 toconform to the anatomical diameter differences of the carotid arteries.This difference can be achieved by a smaller or tapered graft and stentor merely by the restriction of the vessel wall providing a counterforceagainst the stent.

FIG. 10 shows an alternate embodiment of a covered branch stentpositioned in the external carotid artery. The branch stent 100 haspetals 106 similar in configuration and function to the petals of branchstent 80 of FIG. 4 but has a smooth proximal flanged end (shown inphantom) similar to branch stent 90 of FIG. 7. It should be appreciatedthat a branch stent having petals only at its proximal flanged end and asmooth surface at its distal end can also be utilized. Likewise, themain stent can have optionally have petals on the distal end, proximalend or both the distal and proximal ends. The petals preferably flareout so they have a greater diameter than the other graft portions toensure contact with the vessel wall if the vessel wall dilates. Variousconfigurations of the petals are contemplated such as providing anarrowed waist portion and length greater than the waist portion.

FIG. 11 illustrates the main covered stent 70 of FIG. 3 implanted in theleft common and internal carotid arteries. This covered stent 70 can beutilized with any of the aforedescribed covered branch stents.

FIGS. 12-14 illustrate three versions of the stent and associated graftof the present invention. Only a portion of the stent and graft areshown for convenience, it being understood that the stent and graft willhave a sidewall opening, the graft can optionally have petals at theproximal and/or distal end, etc. as in the covered stents described inthe aforementioned embodiments.

FIGS. 13A and 13B reflect the covered stent configuration described inthe FIGS. 1-11 above, but has been provided with new reference numeralsfor convenience. Covered stent 200 of FIG. 13 has an outer graftmaterial or layer 202 and inner stent 204. When stent 204 is expanded,outer graft layer 202 is compressed between the inner stent 204 and thevessel wall.

In FIGS. 12A and 12B, a stent 210 has a graft material or layer 212 onthe inside of the stent 214 as shown. The graft material can be attachedto stent 210, for example, by adhesive, over molding or suture. Whenstent 210 expands, the attached graft material (layer) is carried by theoverlying stent 214 to an expanded condition. The stent 214 is thereforepositioned between the graft 212 and the vessel wall and does not comein contact with the blood. The blood contacts the underlying graftmaterial 212.

In FIGS. 14A and 14B, the covered stent 220 has two layers of graftmaterial, namely outer layer 222 and inner layer 224. The stent 226 caneither be embedded in the graft material layers or attached by variousmethods such as adhesive, over molding or suture. When expanded, theouter layer 222 will be sandwiched between the expanded stent 226 andthe vessel wall and the inner layer 224 will contact the blood andprevent blood contact with stent 226.

FIG. 15 illustrates a stent 300 having a side opening 302 in anintermediate portion. This illustration is provided to show thepositioning of an opening in the stent as described above which wouldalign with the respective opening in the graft of the above-describedembodiments to enable insertion of a branch stent and maintenance ofblood flow through the branching vessel.

FIGS. 16 and 17 illustrate an alternate configuration for treatingbifurcated vessels. A pair of coil spring style stents 602, 612, eachhaving a large diameter region 603, 613 and a smaller diameter region605, 615 are intertwined to form a coil 600. The distal end of thelarger diameter regions terminates at the juncture of the branchingvessel, with the smaller diameter region 605 extending into the mainvessel “x” and the smaller diameter region 615 extending into thebranching vessel “y”. If desired the coils 602, 612 can be used withgraft material. In this case, both smaller diameter regions 605, 615would include graft material, but only one of the larger diameterregions 603, 613 would have graft material to expose the other coiledregion to enable these larger diameter regions to intermesh to securethe coils 602, 612 together.

FIGS. 18-20 illustrate several different tube like stents for treatingbifurcated vessels. These bifurcated stents, shown in their expandedconfiguration, are preferably formed from a tube which is cut, e.g.laser cut, to the configuration shown. One advantage of these bifurcatedstents of FIGS. 18-20 is that they do not change in axial length whenthey are compressed for insertion or change in axial length whenexpanded for placement in the vessel. The bifurcation is shown only inFIG. 18, it being understood that the embodiments of FIGS. 19 and 20 aresimilarly bifurcated.

In the first embodiment of the tubular stents, shown in FIG. 18, stent700 is cut to form a main portion 708 and a bifurcated portion 707extending distally from intermediate region 705 and at an angle to mainportion 708. Stent 700 is shown in the expanded configuration. Stent 700is cut to form a longitudinally extending spine 702 on bifurcatedportion 707 and main portion 708 with a series of radial ribs or loops704 terminating at tips 706. Each of the radial ribs 704 forms a C-shapewith the opposing tips or tangs 706 terminating opposite one another.When compressed, each tip 706 overrides the opposing tip. Additionally,as shown, the tips 706 of ribs 704 of bifurcated portion 707 interleavewith tips 706 of ribs 704 of main portion 708 to reduce thecross-sectional area in the collapsed configuration to aid insertion.Thus, the ratio between the unexpanded delivery configuration and theexpanded configuration is improved.

In the embodiment of FIG. 19, the radial ribs 904, extending from linearspine 902, are offset as shown so the opposing adjacent tips 906interleave, resulting in a smaller cross-sectional area, i.e. smallerdiameter, to facilitate insertion. Only a portion of the main portion ofthe stent is shown, since the remaining main portion, as well as thebifurcated portion, follows the same spine/rib pattern.

In the embodiment of FIGS. 20A and 20B, increased uniform rigidity ofthe tube-like stent 800 is achieved by alternating the radial positionof the spine rather than the continuous linear configuration of spine702 or 902 of stents 700 or 900. FIG. 20B illustrates a segment of thestent 800 (in the expanded configuration) to show the staggering ofspine 802. The remaining portion of the stent 800 follows the samestaggered spine/rib configuration and stent 800 is bifurcated (notshown), i.e. a portion extends distally at an angle to the main portion,in the same manner as tube-like stents 700, 900 to accommodatebifurcated vessels. A transition portion similar to the configuration ofFIG. 18 can optionally be formed in an intermediate region to help formthe bifurcation. As can be seen, the spine 802 has longitudinallyextending segments, for example segments 802 a, 802 b, 802 c, that arespaced both radially and axially. Bifurcated stent 800 is consequentlynot only less flexible then stents 700 and 900 but also is symmetrically(uniformly) flexible in that it will have the same degree of flexibilityin all orientations. Tips 806 of ribs 804 will overlap when stent 800 iscompressed in a similar manner as tip 706 of stent 700. Portions of thestents 700, 800, and 900 of FIGS. 18-20, if desired, can be used withgraft material.

FIGS. 21A and 21B illustrate another embodiment of a bifurcated stent,in the form of a spring like element 650 with a supporting spine 652.The spine 652 is axially and radially staggered similar to the spine ofFIG. 20. However, the stent has a helical spring configuration whichwill elongate when radially compressed and reduce in length whenexpanded. Stent 650 is shown in a compressed configuration with adjacenttips or tangs 656 interleaving in a similar fashion as will tips 906 ofstent 900. Only a portion of the stent 650 is shown, it being understoodthat the remainder of the main portion as well as the bifurcated portionof the stent (which extends at an angle like the bifurcation of thestent of FIG. 18) will have the same spine/rib pattern. A transitionportion similar to the configuration of FIG. 18 can optionally be formedin an intermediate region to help form the bifurcation. Stent 650 can belaser cut from a tube. Portions of the stent 650 can be provided withgraft material.

ALTERNATE APPROACHES

FIG. 22 is a perspective view of an alternative approach to accommodatea branching vessel which utilizes, a pair of juxtaposed covered stentswith angled adjacent ends to accommodate blood flow from a branchingvessel. This is a different approach than the aforedescribed approacheswhich involve implantation and utilization of a stent, either covered oruncovered, having an integral or independently attachable branchextending from the main portion. In the previous approaches, the mainportion was placed in one vessel and the branch extended into abranching vessel to provide fluid communication with the main vessel andbranching vessels.

In the approach of FIG. 22, a pair of covered stents 400, 410 eachhaving angled ends 402, 412 is provided to prevent blocking off thebranching vessel. Covered stent 400 is placed adjacent the juncture ofthe branching vessel, e.g. the common carotid artery “a”, at theupstream end. Covered stent 410 is also placed adjacent the juncture,but extends downstream of the juncture, e.g. into the internal carotidartery “b”. The covered stents 400, 410 preferably abut at edges 404,414, with angled ends 402, 412 extending towards the branching vessel,thereby creating an opening for the passage of blood to the branchingvessel, e.g. the external carotid artery “c.” The angle preferablyranges from about 30 degrees to about 60 degrees, although other anglesto accommodate blood flow are also contemplated. Also, by angling theends of these covered or uncovered stents, intraluminal access to thebranching vessel is enabled. It is also contemplated that a singlecovered or uncovered stent can be utilized, placed upstream of thejuncture, e.g. in the common carotid artery “a”, as shown in FIG. 23, sothe angled end 504 of covered stent 500 will enable blood flow into thebranching vessel, e.g. the external carotid artery “c”.

As can also be appreciated, even though covered stents 400, 410, 500 areshown with underlying stents 406, 416, 516 and overlying graft material408, 418, 518 respectively, the covered stents can alternatively havethe graft material on the inside or both the outside or inside asdescribed above with the other covered stent embodiments.

In yet another approach, stent 300 of FIG. 15 can be used without agraft material and placed in the vessel such that the opening 302 alignswith the lumen (passageway) in the branching vessel. If an uncoveredstent is placed at the juncture of a branching vessel, although bloodflow will not be completely closed off, it will be restricted becausethe blood will need to flow through the links or wires of the stent.Such uncovered stents would also limit future access to the branchingvessel, as described above, because intraluminal access would berestricted by the links or wires. The opening 302 in stent 300 overcomesthese problems. For example, stent 300 can be placed in the commoncarotid artery, extending into the internal carotid artery, across thejuncture of the external carotid artery. The opening 302 can be alignedwith the external carotid artery to allow unobstructed flow between thecommon carotid and external carotid arteries. This may also reduce thebuildup of thrombotic material which might otherwise occur if the bloodflowed through the wire mesh 304 into the external carotid artery.

Stent 300 can also be utilized in another approach wherein it has agraft material, either on the inside, outside, or both the inside andoutside as described above, and is implanted without a branch portion orbranch stent. For example, the stent would extend from the commoncarotid artery into the internal carotid artery. The opening 302 wouldalign with the opening in the graft material and allow fluidcommunication with the branching vessel, e.g. the external carotidartery, as well as intraluminal access to the branching vessel.

While the above description contains many specifics, those specificsshould not be construed as limitations on the scope of the disclosure,but merely as exemplifications of preferred embodiments thereof. Forexample, although use of a single stent is described for the main graftportion, it is also contemplated that more than one stent can beutilized to retain the main graft portion. Additionally, optionallymultiple layers of graft material can be placed on the inside, outsideor both the inside and outside of the stent. Also, the foregoing coveredand uncovered stents of the present invention were described for use incarotid arteries, however as noted above, it is clearly contemplatedthat these covered and uncovered stents can be utilized in other vesselssuch as the coronary arteries, the descending aorta and renal arteries,the external iliac and internal iliac arteries and the common femoraland deep femoral arteries. Those skilled in the art will envision manyother possible variations that are within the scope and spirit of thedisclosure as defined by the claims appended hereto.

1. A system for treating stenosis in a blood vessel comprising: a firstexpandable stent and a first graft overlying the first expandable stent,the first graft having a first lumen for blood flow and having a firstend, a second end, an intermediate portion between the first and secondends, and an opening in the intermediate portion; a second expandablestent and a second graft overlying the second expandable stent, thesecond graft extending at an angle to the first graft and having asecond lumen communicating with the first lumen of the first graft, atleast a portion of the second graft extending through the opening in theintermediate portion of the first graft wherein the first stent has alongitudinally extending spine and axially spaced circumferentiallyextending ribs extending from the spine and the second stent has alongitudinally extending spine and axially spaced circumferentiallyextending ribs extending from the spine, the ribs of the first stentterminate in spaced apart end portions and the ribs of the second stentterminate in spaced apart end portions, the end portions of the ribs ofthe first stent interleaving with the end portions of the ribs of thesecond stent to aid insertion.
 2. The system of claim 1, wherein thelongitudinally extending spine has a plurality of radially and axiallyspaced segments.
 3. The system of claim 1, wherein the first and secondstents are formed from a laser cut tube.
 4. The system of claim 3,wherein adjacent ribs of the first stent are spaced apart to form gapsto receive a portion of ribs of the second stent.
 5. The system of claim1, wherein the circumferential ribs are C-shaped and each include an endportion, the end portions of ribs that are opposite one another areoffset with respect to each other to enable interleaving.
 6. A systemfor treating stenosis in a target blood vessel comprising: a graftportion having a main portion and a branch portion extending therefrom,the main portion having a first end, a second end and an intermediateportion between the first and second ends, the branch portion extendingfrom the intermediate portion at an angle thereto and in fluidcommunication with the main portion; a first stent associated with themain portion and expandable from a first configuration to a secondconfiguration to retain the main portion in position within the targetvessel; and a second stent associated with the branch portion andexpandable from a first configuration to a second configuration toretain the branch portion in position within a branching vessel whereinthe branch portion is integral with the main portion; wherein the firststent has a plurality of ribs having first end portions and the secondstent has a plurality of ribs having second end portions, wherein thefirst end portions interleave with the second end portions to reduce thecross sectional area for insertion.
 7. The system of claim 6, whereinthe first and second stents are positioned within the main and branchportions, respectively, so the main and branch portions expand uponexpansion of their respective stents.
 8. The system of claim 6, whereinthe main and branch portions each include a longitudinally extendingspine.
 9. The system of claim 6, wherein the main and branch portionsinclude a series of spines spaced axially and radially with respect toeach other.
 10. The system of claim 6, wherein the first and secondstents are formed from a laser cut tube.
 11. A system for treatingstenosis in a target blood vessel comprising: a graft having a first endportion, a main portion and a second end portion, the second end portionbeing bifurcated to form a main portion extension and a branch portion,the branch portion and the main portion extension being in fluidcommunication; a first stent positioned within at least the main portionor the first end portion and expandable from a first configuration to asecond configuration to retain the graft in position within the targetvessel wherein the first stent has a longitudinally extending spine andaxially spaced circumferentially extending ribs extending from thespine; and a second stent positioned in the branch portion andexpandable from a first configuration to a second configuration toretain the branch portion in position within a branching vessel; whereineach of the ribs forms a C-shape with opposing end portions terminatingopposite one another and spaced apart from one another.
 12. The systemof claim 11, wherein the first and second stents are formed from a lasercut tube.
 13. The system of claim 11, wherein the second stent includesa plurality of curved ribs each having first and second end portions,the end portions of the ribs of the, first stent are offset with respectto the end portions of the ribs of the second stent.
 14. The system ofclaim 13, wherein end portions of the ribs of the first stent interleavewith end portions of ribs of the second stent.